4K/Green/5200-7200/ ...-Questions

[Kyoko]

Hi,

I've had these questions & i'm sure a lot of people starting out in this do.
So i decided to make a topic so we can get some of these questions answered


-Does 4K really matter? (for ZFS (what i'm personally interested in))

I found this at blowfi.sh (a ZFS nas buildlog)

sub.mesa wrote:
As i understand, the performance issues with 4K disks isn’t just partition alignment, but also an issue with RAID-Z’s variable stripe size.
RAID-Z basically works to spread the 128KiB recordsizie upon on its data disks. That would lead to a formula like:
128KiB / (nr_of_drives – parity_drives) = maximum (default) variable stripe size
Let’s do some examples:
3-disk RAID-Z = 128KiB / 2 = 64KiB = good
4-disk RAID-Z = 128KiB / 3 = ~43KiB = BAD!
5-disk RAID-Z = 128KiB / 4 = 32KiB = good
9-disk RAID-Z = 128KiB / 8 = 16KiB = good
4-disk RAID-Z2 = 128KiB / 2 = 64KiB = good
5-disk RAID-Z2 = 128KiB / 3 = ~43KiB = BAD!
6-disk RAID-Z2 = 128KiB / 4 = 32KiB = good
10-disk RAID-Z2 = 128KiB / 8 = 16KiB = good

So from this i take: 4k doesn't matter that much as long as you use a good number of drives. so that block sizes "match"

- 5200 vs 7200 rpm drives

I've not personally seen numbers but i guess this is obvious:
More rpms = more noice, more heat, higher power consumption & a faster drive.
If anyone has some nice comparisons. I'd love to see them

- "Green" drives

I've heard people say they are bad for raids. I've heard other people say they are perfect for raid.
I'm still looking for a conclusive answer but i don't worry a lot about it.

My Idea with this thread is to have a basic info/sticky topic.
So feel free to answer any of these things, or add your own advice.

 

[OBasel]

sub.mesa posts on here. maybe message him about 4K if he does not see this

5200 is really 5400-5900rpm. the big thing you lose is fast access times which you need with things like sql servers _or_ servers with many users. a good mix with ZFS is green drives + l2arc with ssds but that does not help with writes iirc

green are not the best for raid, some question quality of green drives meeting lower operating requirements

 

[odditory]

No offense but the first post is of all over the road in terms of what information you want. If your questions are about ZFS then this would be the wrong forum.

You might try reworking it into just one or two paragraphs with less commentary about what you're heard, and just state your questions.

 

[Kyoko]

No offense but the first post is of all over the road in terms of what information you want. If your questions are about ZFS then this would be the wrong forum.

You might try reworking it into just one or two paragraphs with less commentary about what you're heard, and just state your questions.

yeh good point. i'll rework it a bit when i get home. This is just the general 'grab' of HDD questions I (& i guess a lot of people) will have. So the idea was to combine those

 

[Metaluna]

- "Green" drives

I've heard people say they are bad for raids. I've heard other people say they are perfect for raid.
I'm still looking for a conclusive answer but i don't worry a lot about it.

There are two issues I can think of with "Green" drives. The first is lack of Time Limited Error Recovery (TLER), which applies to just about any consumer-grade drive. Without going into detail, drives that don't have TLER can behave poorly on many hardware RAID controllers, especially as they age and start developing bad sectors.

The second issue, which is more controversial, and seems to mostly apply to WD drives is the "Load Cycle Count" issue. To save power, the green drives (and possibly others, like laptop drives) will retract (unload) their R/W heads if the drive has been idle for a few seconds. For some reason, many OSes like Linux apparently need to access each drive periodically even if there's no user-requested filesystem activity going on (Windows doesn't do this as much). So what happens is you get situations where the drive will unload the heads after maybe 10 seconds of inactivity, but the OS wants to touch the drive every, say, 20 seconds, which requires the heads to be loaded back onto the platters. So the drive is constantly load-cycling the heads every few seconds. Unfortunately, WD rates their drives for only a few hundred thousand load cycles, and they can add up pretty quickly on a server running 24/7. I don't think anyone can say for sure if this is a real problem that is causing drive failures though. WD doesn't seem too worried about it.

 

[Tegan]

As for TLER, I know that there's a utility that turns TLER on for all connected WD drives (it's called wdtler.exe FYI), but I've never tested it.
I have a couple WD20EARS in a mirror and they work great for media storage, but the performance is terrible when compared to my Black series drives, so I wouldn't use them if you need good performance. Also, I've heard that besides no default TLER, and frequent head-parking, they supposedly present to the OS as 512 instead of 4k sectors which causes problems in Opensolaris (maybe others) so if you aren't using windows, again, rethink the Green drives.

 

[matt_garman]

For what it's worth, Western Digital makes an "enterprise" version of their Green drives, the RE4-GP. The 2TB model is the WD2002FYPS. I could be wrong, but I believe these support TLER, and I think they also have a higher MTBF and longer warranty. But they cost two to three times as much as the consumer-grade drives.

I have five WD20EARS (the cheap consumer version) drives in RAID-6 (using Linux md) for media storage. So far so good, but every week I run a full SMART test as well as a full array check. Of course I bought all five at the same time from the same vendor, and they practically have sequential serial numbers, so if one goes, they'll probably all go. I'd like to replace them with the RE4-GP drives, but just can't justify the expense.

Are there any other vendors producing "enterprise" class low-power drives?

 

[S-F]

You know you can flash the EADS/EARS drives with the RE4-GP firmware? They are the same hardware with different firmware.

 

[matt_garman]

You know you can flash the EADS/EARS drives with the RE4-GP firmware? They are the same hardware with different firmware.

Are you sure about that? This seems like it would be the solution to everyone's WD TLER problems, but I haven't heard of anyone doing this. Doesn't mean it's not true, but it seems to me that if you could flash the cheap EADS/EARS drives with the RE4-GP firmware, a lot more people would be doing it. Although, I suppose it voids your warranty?

Another issue: I haven't been able to determine if the RE4-GP drives use the old 512B sectors, or the new "advanced format" 4K sectors. It seems to me they'd need two RE4-GP firmware variants, one for the 512B drives (EADS) and another for the 4K drives (EARS).

 

[nitrobass24]

Hopefully this will help a lot of people.

I know a lot of people have timeout issues with WD GP drives in RAID and i was talking to one of the techs at LSI and he pointed me to a KB article.
Apparently the RE4 drives had the same problems so WDC released a new firmware 04.05G05 to fix the issues.

Firmware Release notes
Firmware and instructions for LSI

You will need to connect each drive to a mobo SATA port for the flash, but some controller manufacturers can manipulate the .bin(firmware) file for you so you can flash all your drives at the same time so you dont have to break your RAID.

Also this is supposed to be a non-destructive flash, but as a precaution it is best to backup your data first!

PS: The LSI tech also told me that this firmware will work on non-RE4 (WD20EADS) drives as well. Apparently the hardware is a 100% match. Go figure

 

[Patrick]

If someone successfully does the flash and a write-up I would make this a front page post.

 

[nitrobass24]

Treadstone flashed 50 of his 2TB drives

 

[ACCS]

As for TLER, I know that there's a utility that turns TLER on for all connected WD drives (it's called wdtler.exe FYI), but I've never tested it.

This doesn't work on the newest WD desktop drives.

 

[brendanz]

My apologies for digging up such an old thread (12 months old to the day), but I had a question about this drive and the LSI 9260-8i controller.

I have just read this thread on Hardforum as well http://hardforum.com/showthread.php?t=1285254

Basically, I am in the unfortunate position of having six WD20EARS hard drives. I was planning on building a RAID6 array out of these for home use.

I'm not really fussed about the performance of the array to be honest, however the data redundancy is important. I understand that this drive does not support TLER, even with flashing custom firmware/etc. I understand this can have an impact on the RAID array with many controllers, with the drives dropping off the RAID and requiring work to get it back up again.

So, my question: even with a good controller like the LSI 9260-8i, is it advisable to run these drives in a RAID 5 or 6 configuration? Can I adjust a certain setting to make it worthwhile? Or should I simply just not even bother and replace them?